You mention two telephony lines were used for comms between station and site. Was the quality of audio for remote broadcasts better than a typical phone call?
The response of a twisted pair was pretty good over 2 to 4 miles as I recall but for a audio grade (50Hz to 5000Hz) various techniques were used that at the simplest involved coils but there were also active equalizers available for long haul circuits and/or "hi-fi" requirements. Remember DSL lines were/are shipping 1..2Mhz carriers over those same old telco lines. :-)
Of course some old trunk lines used paper insulation. Really. Which meant noise went up ... when it rained.